拉瓦尔喷管外发生激波反射工况详细分析

平面拉瓦尔喷管的环境压力与入口总压的比值从设计工况到第三极限工况(管口处为正激波)逐渐增大时,喷管外的激波现象不同.根据已知的激波反射理论,将设计工况到第三极限工况间的工作状况进一步细分为强斜激波工况、马赫反射工况、双解区和正规反射工况、并将由气流偏转角所表示的发生正规反射和马赫反射的条件用环境压力与总压的比值来表示,找出了强、弱斜激波的环境压力与总压比值的临界值,得到这些临界值随着喷管面积比的变化趋势.最后针对面积比为5的平面拉瓦尔喷管,由理论分析得到其管外发生正规反射、马赫反射、强斜激波反射时对应的压比分别为:0.0841,0.0959和0.2005,并用数值模拟来验证理论分析的正确性. 

Further detailed analysis about shock wave reflection outside Laval nozzle in different working states

When ratio of environmental pressure to total pressure increases from design state to third limit condition (normal shock at the outlet of nozzle), there are different shock wave phenomena outside the Laval nozzle. According to extant theory about shock wave reflection, the working range between design condition and the third limit condition was subdivided into several sections: strong oblique shock wave condition, Mach reflection condition, regular reflection and dual solution domain. Three critical ratios of environmental pressure to total pressure were proposed and determined to replace flow-deviation angle for estimating different Laval nozzle working statuses. Varying tendency of these critical ratios of Laval nozzle in various aspect ratios were also given with a figure. The pressure ratios corresponding regular reflection, Mach reflection and strong oblique wave in a planar Laval nozzle with aspect ratio 5 were 0.0841, 0.0959 and 0.2005 respectively, and then the accuracy of these values were verified with numerical simulation.